1. Field of the Invention
This invention relates generally to the field of manufacturing corner joints, and in particular, to methods and apparatus for manufacturing splined corner joints with a novel fixture for holding workpieces and guiding a routing tool or the like.
2. Prior Art
Corner joints in wood structures have often been manufactured with interlocking structure of one sort or another formed integrally with the edges of the workpieces to be joined. Perhaps the most popular of such joints, as well as the most attractive, is the dovetail joint. Dovetail joints can be particularly difficult to manufacture, as the end of one workpiece must be provided with dovetail-shaped projection, whereas the end of the another workpiece must be provided with slots of corresponding cross-section. Moreover, the mating projections and slots must be precisely aligned with respect to the sides or lateral edges of the workpieces.
Fixtures for manufacturing dovetail corner joints in particular, and other kinds of joints in general, are known in the art. It is common for such fixtures to include guide slots formed by various structure for guidably supporting a routing tool or the like, such tools being used to cut out the projections and the slots. In each instance, however, separate fixtures, or portions of fixtures or sets of guide slots must be utilized for each workpiece. In other words, a first set of guide slots and accompanying workpiece clamping means are used to form the end with the projections, and another set of guide slots and clamping means, different than the first set, is used to form slots in the end of the other workpiece. Examples of such fixtures may be found in the following U.S. Pat. Nos.: 2,764,191; 3,109,466; 3,878,875; 3,604,484; 3,606,916; 4,163,465; 4,168,730; and, 4,405,004.
The method and apparatus for manufacturing corner joints taught herein overcomes all of the difficulties encountered in the prior art methods and apparatus. Firstly, corner joints are held together primarily by splines, that is, separate wedge-shaped members which fit into corresponding slots in both edges of the workpieces to be joined together. Although this invention preferably utilizes a worktable having a plurality of substantially parallel finger slots therethrough for guidably supporting a routing tool or the like on one surface thereof, it is the first such apparatus which provides clamping means disposed on the other surface of the worktable for receiving and holding both workpieces simultaneously, wherein mitered edges of the workpieces to be joined together are held against one another in that very orientation which is desired for the final product. In other words, the workpieces are clamped together in a predetermined alignment relative to one another in a completed or finished orientation during formation of the grooves. Accordingly, when the workpieces are removed from the fixture for permanent attachment to one another, they automatically align perfectly with one another. Splines of a cross-section corresponding to that of the slots, can then be slidably inserted into the slots, locking the workpieces together. The joint can be finished by cutting unnecessary portions of the spline, and then filing and sanding the exposed ends thereof to be flushed and smooth with the surfaces of the workpieces. Such corner joints can be easily made with a dovetail configuration, or alternatively, with almost any cross-section, limited only by the available shapes of the cutting blades of routing tools and the like.
The corner joint which is produced according to this invention is very strong, automatically and precisely aligned and quite attractive. Corner joints according to this invention are also considerably easier and faster to manufacture, thereby reducing costs.